Ok, although there are conditions during the daylight in which interior lights are necessary. (shadows, garage, etc)
In PQ25 the electrical supply for the interior lights (dome, glove box, trunk, etc) is made by the same wire, so individual coding is not possible. The operation of each of the interior lights is conditioned according to how the ground wire is connected.
Installing the cruise control is easy compared to the electrical installations you have already done.
6C0953513B "is not possible" in OEM way.
The best thing you can do for your future retrofits is to buy the
original VCDS, someday you will remember that I warned/recommended you.
You will need it to erase intermittent failures when modifications are made, etc, etc, etc... IMHO it is better not to depend on your friend for this.